Proximity fuze



Jan. 9, 1968 K, o. LAGERSTRGM ET AL 3,362,330

PROXIMITY FUZE Filed March 14, 1966 INVENTORS KARL OLOFGU/V/VARLAGERSTRUM 60574 WOLK JOH/VFREDR/ LF HART/MANN United States PatentOffice 3,362,330 Patented Jan. 9, 1968 3,362,330 PROXIMITY FUZE KarlOlof Gunnar Lagerstriim, Eskilstuna, Giista Wolke,

Jakobsherg, and John Fredrilr Alf Hartmann, Steel;- liolm, Sweden,assignors to Forsvarets Fabriksverk, Eskilstuna, Sweden Filed Mar. 14,1966, Ser. No. 534,066 6 Claims. (U. 102-702) ABSTRACT OF THE DISCLOSUREProximity fuze in which an electrical circuit for determining the firingsensitivity of the proximity fuze includes a number of series orparallel connected impedance elements located inside the envelope of thefuze. Control conductors connected in the sensitivity circuit and to theimpedance elements have continuous parts which penetrate the wall of theenvelope through insulation members providing electrical insulation fromthe remainder of the envelope and from each other. The connection ofeach conductor and its associated impedance element in the sensitivitycircuit provides a predetermined impedance influence or absence of suchinfluence on the sensitivity circuit by the associated impedanceelement, which influence or its absence is changed by an interruption ofthe associated conductor. A part of each conductor is located at or justunder the outer surface of the envelope insulation members and that partof each conductor can be broken, out or otherwise interrupted, e.g., bymeans of a knife or similar tool, to change the impedance and hencesensitivity setting of the sensitivity circuit without gaining access tothe interior of the fuze.

Cross reference to related application Co-pending application Ser. No.534,067, filed on Mar. 14, 1966 relates to a different construction andmethod for changing the influence of impedance elements on proximityfuze electrical sensivity circuits without gaining physical access tothe interior of the fuze envelope.

Background The present invention relates to a proximity fuze for aprojectile, such as a bursting shell, which makes the projectiledetonate shortly before it hits the target. The proximity fuze radiatesenergy in the form of electromagnetic waves or sound waves. A part ofthe radiated energy is reflected from the target, returns to and isreceived by the proximity fuze. When the received energy reaches apredetermined level the fuze ignites the charge in the projectile.

The amount of received reflected energy is greatly dependent on thereflecting power of the target. If the ground is the target, thereflecting power depends upon the character of the terrain andtherefore, the distance from the target at which a projectile with apre-set proximity fuze detonates, will vary for different kinds oftarget terrain. The distance where detonation occurs is also influencedby the angle of the direction of movement of the projectile inconjunction with terrain surface, also by the speed of the projectile,and whether or not there is a wood or woods on the target terrain.

The distance from the target at which detonation should take place inorder to obtain the best possible effect is dependent on the protectinglevel of the target on the angle between the direction of movement ofthe projectile and the target level and on the capacity of the terrainto prevent the spreading of projectile splinters. For each type ofprojectile the distance from the target at which detonation shouldoccur, in order to cause maximum damage, has a specific value. Thedamage caused by the projectile when exploded at the desirable specificdistance is frequently many times greater than if the projectile isexploded at other distances, which could be rather close to the specificdistance.

Before each shot it may as a rule be possible to find out or to estimatethe reflecting power and the character of the terrain, such as thepresence of wood, and also the protecting level of the target. It mayalso be possible to know or estimate the speed of the projectile, theangle between the direction of movement of the projectile and the levelof the target, and also the specific explosion distance for maximumdamage. Therefore, it is possible to increase the effect of theexpenditure of ammunition if the proximity fuze of each projectile iscapable of being adjusted immediately before the firing, so that eachprojectile may explode at the desired specific distance and maximumdamaging effect will be obtained.

The adjustability may be continuous or non-continuous. Generally thecharacteristics of the fuze may be changed by adjusting an impedance,such as a resistance, in the electric circuit of the proximity fuze, forexample in its amplifier part. It is also possible to change themagnitude of the transmitted energy or to adjust the sensitivity of thereceiving means. If a continuous adjustability is wanted, for example inthe form of a continuously adjustable potentiometer, special steps haveto be taken to ensure a good contact-making in consideration of theforming of oxide on the contact making parts during storage. Further,there should be way to effectively prevent the adjustment of thepotentiometer from being influenced by the rotation of the projectile.There is a device known for this purpose (U.S. Patent 2,552,482) but itis rather complicated.

Summary Calculations have shown that it is sufiicient to provide anadjustability of the characteristics of the proximity fuze in ten stepsor less, in order to obtain a correct adjustment of the distance atwhich detonation should take place for achieving the maximum damage.

One object of the present invention is to provide a proximity fuze whichis adjustable in steps. This adjustability means that thecharacteristics of the fuze may be altered in steps, so that the desireddistance from the target for detonation may be approximately obtained.By a stepwise adjustment a simpler and more rigid construction can beobtained than by a continuous adjustability.

Another object of the invention is to provide such a stepwiseadjustability by enabling an impendance to be adjusted without any needfor disassembling the fuze .or to make any incision in the fuze or toinfluence the aerodynamic characteristics of the projectile.

A further object resides in the provision of a proximity fuze accordingto the invention having a number of impedance elements connected inseries or in parallel in a circuit for adjusting the sensitivity of thefuze, the impedance elements being located inside the envelope of thefuze and connected to conductors which penetrate the wall of saidenvelope and insulated from said envelope by means of an insulationmember, the outer surface of which is in level with the outer surface ofthe envelope. A part of each of the conductors is located at or justbeneath said outer surface of said insulation member. When the impedanceelements are connected in series, each of the conductors is connected inparallel to one of the elements so as to provide a short circuit pathfor the latter. When the impedance elements are connected in parallel,each of the conductors is connected in series with one of the impedanceelements. The part of each conductor which is located at or just beneaththe outer surface of the insulation member can be cut off by means of aknife or a simi lar tool.

Further objects and features of the proximity fuze according to theinvention will become apparent from the following description and claimsand from the accompanying drawing, in which FIGS. 1 and 3 illustratesimplified circuit diagrams of two embodiments of the present invention,and

FIG. 2 illustrates a section through the envelope of a proximity fuzeand shows how the conductor shunted across one of the impedance elementsof FIGURE 1 can be situated adjacent the exterior surface of the fuzeaccording to the invention.

In the embodiment according to FIG. 1 a number of impedance elements 1are connected in series in an electrical circuit, such as a part of apotentiometer (not shown), by means of which the sensitivitycharacteristics of the proximity fuze are determined. Each impedanceelement 1 is shunted by a conductor 2. As illustrated in FIG. 2, whereonly one of the plurality of impedance elements is shown, each impedanceelement 1 is located inside an envelope 4 enclosing the fuze. Eachconductor 2 penetrates the wall of said envelope 4 and is insulated fromthe latter by means of an insulating member 3. The outer surface ofinsulating member 3 is level with and follows smoothly the outer surfaceof the rest of the envelope 4. A part of each conductor 2 is located ator just under the outer surface of the insulating member 3. Theinsulating member 3 is preferably made from a soft material, such as asynthetic resin of a suitable kind. This makes it possible to cutthrough one or more of the shunting conductors 2 by means of a knife ora similar tool, which will influence the characteristics of theproximity fuze.

In the second embodiment according to FIG. 3 a number of impedanceelements 5 are connected in parallel in an electrical sensitivitycircuit within the proximity fuze of the same kind as described inconnection with FIG. 1. Also, in this case, each impedance element 5 islocated inside the envelope 4 of the fuze. Each conductor 6, leading toone of the elements 5, is, however, penetrating the wall of saidenvelope 4 and is insulated from the latter by means of an insulatingmember 3 of the kind illustrated in FIG. 2. A part of each conductor 6is located at or just under the level of the outer surface of theinsulating member 3 in a manner similar to the arrangement shown in FIG.2.

The cutting off of or breaking of the exteriorly located part of one ormore of the conductors 6 will influence the impedance characteristicsand hence sensitivity of the sensitivity circuit of the proximity fuzein the way indicated above.

By cutting off the exterior parts of one or more of the conductors 2. or6 before the shot is fired it is possible to adjust the distance fromthe target at which the explosion of the projectile is going to takeplace, in order to get the maximum damaging efiect of the explosion.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiments are therefore to be considered in all respects asillustrative and no restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by Letters Patent is:

1. In combination in a proximity fuze which comprises an envelope and anelectrical circuit for determining the firing range sensitivity of theprox mity fuze, the improvement comprising: a plurality ofinterconnected impedance elements located inside of said envelope andconnected in said sensitivity circuit; and a plurality of conductors,each of which is associated and connected in circuit with a specific oneof said impedance elements in said sensivity circuit so that continuityof each of said conductors controls the effect of its associatedimpedance element on the impedance of the sensitivity circuit; each ofsaid conductors having a portion, intermediate its connections to saidsensitivity circuit, which penetrates said envelope so that a part ofthe conductor is disposed immediately adjacent the envelope exteriorsurface; the portions of said envelope penetrated by said conductorsconstituting electrically insulating means which insulate said conductorportions; said conductor portions providing exteriorally accessiblecontrol means by which the impedance effect of each of said impedanceelements on said sensitivity circuit can be changed.

2. The combination as defined in claim 1 wherein said plurality ofimpedance elements are connected in series with each other in saidsensitivity circuit; each of said conductors is shunt connected acrossan associated said impedance element; and an intermediate extent of eachsaid conductor, between its shunt connections, passes into and back outof at least a part of said insulating means with a portion of saidconductor disposed adjacent the exterior surface of the associated partof said insulating means.

3. The combination as defined in claim 1, wherein said plurality ofimpedance elements are connected in parallel with each other in saidsensitivity circuit; each of said conductors is connected from one endof and in series with an associated said impedance to one side of saidparallel connection; and an intermediate extent of each said conductor,between its series connections, passes into and back out of at least apart of said insulating means with a portion of said conductor disposedadjacent the exterior surface of the associated part of said insulatingmeans.

4. The combination as defined in claim 1, wherein said conductorportions penetrate into and through said envelope and a part thereof isexterior of and is disposed against the exterior surface of saidinsulating means.

5. The combination as defined in claim 1, wherein said insulating meansis made from soft material and conductor portions which penetrate saidenvelope are embedded in said insulating means with a part thereofclosely adjacent but below the exterior surface of said insulatingmeans.

6. The combination as defined in claim 1 wherein the exterior surface ofsaid insulating means is smoothly contoured with the exterior surface ofthe remainder of said fuze envelope.

References Cited UNITED STATES PATENTS 1,791,606 2/1931 Ruhlemann10270.2 2,552,482 5/1951 Ferris et al. 102-70.2 2,959,128 11/1960 Boykin10270.2 3,048,136 8/1962 Holmes 102--70.2 X 3,166,015 1/1965 Tuve et a1.102-702 V BENJAMIN A. BORCHELT, Primary Examiner.

W. C. ROCH, V. R. PENDEGRASS,

Assistant Examiners.

